WASHINGTON {AP} Ever since Woodrow Wilson, presidents have cozied up to popes. Lyndon Johnson lobbied a pope to back him on Vietnam. Ronald Reagan, once caught dozing during a papal address, talked Cold War tactics with a pope.

Now it's President Bush's turn to court the Vatican. He sees Pope John Paul II on Monday as he contemplates one of the most vexing questions of his presidency: Should the government sponsor promising medical research on stem cells extracted from human embryos?

The president is still weighing the moral and ethical  and political  ramifications of funding embryonic stem cell research.

Proponents believe embryonic stem cell research might yield treatments for people suffering with illnesses such as diabetes and Alzheimer's disease.

Yet Bush knows that deciding to pay for the research would put him at odds with the right wing of his party and the Vatican. The Roman Catholic Church is opposed to this research because human embryos are destroyed in the process.

"This is an issue that speaks to morality and science," he said.

Bush says politics won't sway his decision, yet the potential for political fallout is great.

The president, who has been wooing the Catholic vote since taking office, hasn't said whether he'll broach the touchy stem cell issue with the pope.

If Bush doesn't bring it up, the pope will, said John White, professor of politics at Catholic University of America. "I have no doubt that this particular pope is going to bring this issue up head on," White said.

American presidents didn't always seek an audience with the pope.

Woodrow Wilson and Dwight Eisenhower both visited the pope, but generally anti-Catholic sentiment was just strong enough in America that presidents were wary about aligning themselves with the pontiff. John Kennedy, the first Catholic president, ignored that taboo, as has every president since then.

Johnson decided to visit Pope Paul VI in December 1967, at the end of a three-day whirlwind tour of five nations, because he was worried the pope's New Year's Day address would attack the United States and its policy in Vietnam, said Gerald Fogarty at the University of Virginia. Before the meeting, Johnson sent the pope a 10-page memo of his views about the war and his search for peace.

Richard Nixon and Gerald Ford visited Paul VI too.

John Paul II, who became pope in October 1978, a year later became the first pontiff to set foot in the White House. Jimmy Carter welcomed him.

"This was an important moment as a pious Georgia Baptist welcomed the pope to the White House," said George Weigel, a papal historian in Washington.